Morphological and Ultrastructural Changes in Tissues of Intermediate and Definitive Hosts Infected by Protostrongylid Lungworms (Nematoda: Metastrongyloidea)

Authors: KUCHBOEV, ABDURAKHIM - Institute Of Zoology - Uzbekistan; Hoberg, Eric

Submitted to: Turkish Journal of Zoology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/13/2010
Publication Date: 4/1/2010
Citation: Kuchboev, A., Hoberg, E.P. 2010. Morphological and Ultrastructural Changes in Tissues of Intermediate and Definitive Hosts Infected by Protostrongylid Lungworms (Nematoda: Metastrongyloidea). Turkish Journal of Zoology. 35:1-7.

Interpretive Summary: Lungworm parasites in ruminants have complex life cycles where adult parasites occupy pulmonary tissues, and produced infective larvae which develop in molluscan intermediate hosts. Cycles are completed when infective stages in mollusks, or which are free in the environment, are ingested by ungulates while foraging. The physiological impact on ungulates is caused by damage to the lungs by both adult and larval parasites in ungulate hosts. Understanding the mechanisms involved in host responses to parasitism promotes potential pathways to moderate the damage caused by these parasites. Cellular and sub-cellular mechanisms involved in tissue responses to larval and adult lungworms (Protostrongylidae) were respectively explored through experimental and natural infections in molluscan intermediate (Xeropicta candacharica) and ruminant definitive hosts (Ovis aries). Reaction to developing larval stages in the gastropod is manifested as cellular infiltration involving lymphocytes and macrophages into the infected tissue which restricts damage and may result in destruction and elimination of parasites from the intermediate host. Variations in the patterns of localization for infective third-stage larvae in the foot tissue of the intermediate host are described. In the definitive host, evaluation of lung tissue by histology and transmission electron microscopy revealed the activation of lymphocytic and monocytic-macrophage systems. An intensive fibroblastic reaction in the lung parenchyma results in formation of connective-tissue capsules around helminths and more broadly demarcates zones of infected tissue. These observations contribute to a basic knowledge of pathogenesis related to parasitic infection in mammalian and invertebrate hosts.

Technical Abstract: Cellular and sub-cellular mechanisms involved in tissue responses to larval and adult lungworms (Protostrongylidae) were respectively explored through experimental and natural infections in molluscan intermediate (Xeropicta candacharica) and ruminant definitive hosts (Ovis aries). Reaction to developing larval stages in the gastropod is manifested as cellular infiltration involving lymphocytes and macrophages into the infected tissue which restricts damage and may result in destruction and elimination of parasites from the intermediate host. Variations in the patterns of localization for infective third-stage larvae in the foot tissue of the intermediate host are described. In the definitive host, evaluation of lung tissue by histology and transmission electron microscopy revealed the activation of lymphocytic and monocytic-macrophage systems. An intensive fibroblastic reaction in the lung parenchyma results in formation of connective-tissue capsules around helminths and more broadly demarcates zones of infected tissue.